System and method for collecting plasma

ABSTRACT

A method for collecting plasma includes determining the weight and hematocrit of a donor, and inserting a venous-access device into the donor. The method then withdraws blood from the donor through a draw line connected to a blood component separation device, and introduces anticoagulant into the withdrawn blood. The blood component separation device separates the blood into a plasma component and a second blood component, and the plasma component is collected from the blood component separation device and into a plasma collection container. The method may then calculate (1) a percentage of anticoagulant in the collected plasma component, and (2) a volume of pure plasma collected within the plasma collection container. The volume of pure plasma may be based, at least in part, on the calculated percentage of anticoagulant. The method may continue until a target volume of pure plasma is collected within the plasma collection container.

PRIORITY

This patent application is a continuation of and claims priority fromU.S. application Ser. No. 17/205,374, filed Mar. 18, 2021, entitled“System and Method for Collecting Plasma,”, and naming Michael Ragusa asinventor, the disclosure of which is incorporated herein, in itsentirety by reference.

U.S. application Ser. No. 17/205,374, in turn, is a continuation of andclaims priority from U.S. application Ser. No. 16/866,078, filed May 4,2020, entitled “System and Method for Collecting Plasma,” now U.S. Pat.No. 10,980,926, and naming Michael Ragusa as inventor, the disclosure ofwhich is incorporated herein, in its entirety by reference.

U.S. application Ser. No. 16/866,078, in turn, is a continuation of andclaims priority from U.S. application Ser. No. 15/608,183, filed May 30,2017, entitled “System and Method for Collecting Plasma,” now U.S. Pat.No. 10,758,652, and naming Michael Ragusa as inventor, the disclosure ofwhich is incorporated herein, in its entirety by reference.

TECHNICAL FIELD

The present invention relates to systems and methods for bloodapheresis, and more particularly system and methods for collecting aplasma product.

BACKGROUND ART

Apheresis is a procedure in which individual blood components can beseparated and collected from whole blood temporarily withdrawn from asubject. Typically, whole blood is withdrawn through a needle insertedinto a vein of the subjects arm and into a cell separator, such as acentrifugal bowl. Once the whole blood is separated into its variouscomponents, one or more of the components (e.g., plasma) can be removedfrom the centrifugal bowl. The remaining components can be returned tothe subject along with optional compensation fluid to make up for thevolume of the removed component. The process of drawing and returningcontinues until the quantity of the desired component has beencollected, at which point the process is stopped. A central feature ofapheresis systems is that the processed but unwanted components arereturned to the donor. Separated blood components may include, forexample, a high density component such as red blood cells, anintermediate density component such as platelets or white blood cells,and a lower density component such as plasma.

Many jurisdictions have regulations regarding the amount of whole bloodand/or blood components that can be removed from a donor. For example,the U.S. Food and Drug Administration (“the FDA”) sets both an upperlimit on the volume of plasma that may be collected (e.g., 800 ml for anadult weighing more than 175 pounds) as well as an upper limit on thetotal collection volume (e.g., 880 ml for an adult weighing more than175 pounds). Prior art plasma collection systems are unable to determinethe total volume of plasma that has been collected (e.g., because theproduct collected is a mixture of plasma and anticoagulant) and,therefore collect based on the total collection volume, even if thetotal volume of plasma that has been collected is below the limitprescribed by the FDA.

SUMMARY OF THE INVENTION

In accordance with some embodiments of the present invention, a methodfor collecting plasma includes determining the weight and hematocrit ofa donor, and inserting a venous-access device into the donor. Once thevenous access device is inserted, the method may withdraw whole bloodfrom the donor through the venous-access device and a draw line that isconnected to a blood component separation device. The method may thenintroduce anticoagulant into the withdrawn whole blood through ananticoagulant line and separate, using the blood component separationdevice, the withdrawn whole blood into a plasma component and at least asecond blood component. Once separated, the plasma component may becollected from the blood component separation device and into a plasmacollection container. During processing, the method may calculate (1) apercentage of anticoagulant in the collected plasma component, and (2) avolume of pure plasma collected within the plasma collection container.The volume of pure plasma may be based, at least in part, on thecalculated percentage of anticoagulant in the collected plasmacomponent. The method may continue the process (e.g., withdrawing wholeblood, introducing anticoagulant into the whole blood, separating theblood, collecting the plasma, and calculating the percentage ofanticoagulant and volume of pure plasma) until a target volume of pureplasma is collected within the plasma collection container.

In some embodiments, the method may determine a change in volume withinan anticoagulant container, and the calculated percentage ofanticoagulant in the collected plasma may be based, at least in part, onthe change in volume within the anticoagulant container. Additionally oralternatively, the method may determine a volume of anticoagulantintroduced into the whole blood based on a number of rotations of ananticoagulant pump. In such embodiments, the calculated percentage ofanticoagulant in the collected plasma may be based, at least in part, onthe number of rotations of the anticoagulant pump. The method may alsodetermine a volume of anticoagulant within the blood componentseparation device, and the calculated percentage of anticoagulant in thecollected plasma may be based, at least in part, on the volume ofanticoagulant within the blood component separation device.

In further embodiments, the method may monitor the volume and/or weightof the plasma component collected within the plasma collection container(e.g., using a weight sensor), and the calculated volume of pure plasmacollected within the plasma collection device may be based, at least inpart, on the monitored volume and/or weight of the collected plasmacomponent. Additionally or alternatively, determining the hematocrit ofthe donor may include monitoring a volume of red blood cells collectionwithin the blood separation device. In such embodiments, the determinedhematocrit of the donor may be based, at least in part, on the monitoredvolume of red blood cells collected within the blood separation deviceand the volume of whole blood withdrawn from the donor.

The target volume of pure plasma may be based, at least in part, on theweight of the donor. The percentage of anticoagulant in the collectedplasma component may include at least a portion of the anticoagulantintroduced into the withdrawn blood and at least a portion of a volumeof anticoagulant that is added to the system during a priming step.After collecting at least a portion of the target volume of pure plasma,the method may return the second blood component to the donor through areturn line.

In accordance with additional embodiments, a system for collectingplasma includes a venous-access device for drawing whole blood from asubject and returning blood components to the subject, and a bloodcomponent separation device for separating the drawn blood into a plasmacomponent and a second blood component. The blood component separationdevice has an outlet and is configured to send the plasma component to aplasma container. The system may also include a blood draw line fluidlyconnected to the venous-access device and an anticoagulant lineconnected to an anticoagulant source. The blood draw line transportsdrawn whole blood to the blood component separation device, and the flowthrough the blood draw line may be controlled by a blood draw pump. Theanticoagulant line may introduce anticoagulant into the drawn wholeblood.

Additionally, the system may include a controller that controls theoperation of the centrifuge bowl. The controller may also calculate (1)a percentage of anticoagulant in the collected plasma component, and (2)a volume of pure plasma collected within the plasma container. Thevolume of pure plasma may be based, at least in part, upon thepercentage of anticoagulant in the collected plasma component. Thecontroller may stop the blood draw pump when a target volume of pureplasma (e.g., based, at least in part, on the weight of the donor) iscollected within the plasma container. In some embodiments, thepercentage of anticoagulant in the collected plasma component may bebased, at least in part, on the volume of anticoagulant added to thedrawn whole blood and the subject's hematocrit.

The system may also include an anticoagulant source weight sensor thatmeasures the weight of the anticoagulant source. The controller maymonitor the change in volume within the anticoagulant container based onthe measured weight of the anticoagulant source, and the calculatedpercentage of anticoagulant in the collected plasma may be based, atleast in part, on the change in volume within the anticoagulant source.Additionally or alternatively, the controller may monitor the number ofrotations of an anticoagulant pump to determine a volume ofanticoagulant introduced into the whole blood. In such embodiments, thecalculated percentage of anticoagulant in the collected plasma may bebased, at least in part, on the number of rotations of the anticoagulantpump.

In some embodiments, the system may include an optical sensor located onthe blood component separation device. The optical sensor may monitorthe contents of the blood component separation device and determine if avolume of anticoagulant remains within the blood component separationdevice. The calculated percentage of anticoagulant in the collectedplasma may be based, at least in part, on the volume of anticoagulantwithin the blood component separation device.

In additional embodiments, the system may also include a plasmacontainer weight sensor that monitors a volume and/or weight of theplasma component collected within the plasma collection container. Thecalculated volume of pure plasma collected within the plasma collectioncontainer may be based, at least in part, on the monitored volume and/orweight of collected plasma component. The system may also have anoptical sensor located on the blood component separation device. Theoptical sensor may monitor the volume of red blood cells collectedwithin the blood separation device. The controller may then determinethe subject's hematocrit based, at least in part, upon on the monitoredvolume of red blood cells collected within the blood separation deviceand the volume of whole blood withdrawn from the donor. The percentageof anticoagulant in the collected plasma component may include at leasta portion of the anticoagulant introduced into the withdrawn blood andat least a portion of a volume of anticoagulant added to the systemduring a priming step.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, in which:

FIG. 1 schematically shows a perspective view of a blood processingsystem in accordance with some embodiments of the present invention.

FIG. 2 schematically shows a top view of the blood processing system ofFIG. 1 , in accordance with some embodiments of the present invention;

FIG. 3 schematically shows a disposable set installed within the bloodprocessing system of FIG. 1 , in accordance with some embodiments of thepresent invention.

FIG. 4 is a flowchart depicting a method of collecting plasma, inaccordance with embodiments of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Illustrative embodiments of the present invention provide bloodprocessing systems and methods for collecting a target volume of pureplasma. The system and method calculate a percentage of anticoagulantcollected within a plasma collection container (e.g., in addition to theplasma that is collected within the container) based on the amount ofanticoagulant added to the system and the hematocrit of the donor. Thesystem/method may then calculate the volume of pure plasma (e.g., plasmawithout anticoagulant) that has been collected within the container.Details of the illustrative embodiments are discussed below.

As shown in FIGS. 1 and 2 , the blood processing system 100 includes acabinet 110 that houses the main components of the system 100 (e.g., thenon-disposable components). Within the cabinet 110, the system 100 mayinclude a first/blood pump 232 that draws whole blood from a subject,and a second/anticoagulant pump 234 that pumps anticoagulant through thesystem 100 and into the drawn whole blood. Additionally, the system 100may include a number of valves that may be opened and/or closed tocontrol the fluid flow through the system 100. For example, the system100 may include a donor valve 120 that may open and close to selectivelyprevent and allow fluid flow through a donor line 218 (e.g., an inletline; FIG. 3 ), and a plasma valve 130 that selectively prevents andallows fluid flow through an outlet/plasma line 222 (FIG. 3 ). Someembodiments may also include a saline valve 135 that selectivelyprevents and allows saline to flow through a saline line 223.

To facilitate the connection and installation of a disposable set and tosupport the corresponding fluid containers, the system 100 may includean anticoagulant pole 150 on which the anticoagulant solution container210 (FIG. 3 ) may be hung, and a saline pole 160 on which a salinesolution container 217 (FIG. 3 ) may be hung (e.g., if the procedurebeing performed requires the use of saline). Additionally, in someapplications, it may be necessary and/or desirable to filter the wholeblood drawn from the subject for processing. To that end, the system 100may include blood filter holder 170 in which the blood filter (locatedon the disposable set) may be placed.

As discussed in greater detail below, apheresis systems 100 inaccordance with embodiments of the present invention withdraw wholeblood from a subject through a venous access device 206 (FIG. 3 ) usingthe blood pump 232. As the system 100 withdraws the whole blood from thesubject, the whole blood enters a blood component separation device 214,such as a Latham type centrifuge (other type of separation chambers anddevices may be used, such as, without limitation, an integralblow-molded centrifuge bowl, as described in U.S. Pat. Nos. 4,983,158and 4,943,273, which are hereby incorporated by reference). The bloodcomponent separation device 214 separates the whole blood into itsconstituent components (e.g., red blood cells, white blood cell, plasma,and platelets). Accordingly, to facilitate operation of the separationdevice 214, the system 100 may also include a well 180 in which theseparation device 214 may be placed and in which the separation device214 rotates (e.g., to generate the centrifugal forces required toseparate the whole blood).

To allow the user/technician to monitor the system operation andcontrol/set the various parameters of the procedure, the system 100 mayinclude a user interface 190 (e.g., a touch screen device) that displaysthe operation parameters, any alarm messages, and buttons which theuser/technician may depress to control the various parameters.Additional components of the blood processing system 100 are discussedin greater detail below (e.g., in relation to the system operation).

FIG. 3 is a schematic block diagram of the blood processing system 100and a disposable collection set 200 (with an inlet disposable set 200Aand an outlet disposable set 200B) that may be loaded onto/into theblood processing system 100, in accordance with the present invention.The collection set 200 includes a venous access device 206 (e.g., aphlebotomy needle) for withdrawing blood from a donor's arm 208, acontainer of anti-coagulant 210, a centrifugation bowl 214 (e.g., ablood component separation device), a saline container 217, and a finalplasma collection bag 216. The blood/inlet line 218 couples the venousaccess device 206 to an inlet port 220 of the bowl 214, theplasma/outlet line 222 couples an outlet port 224 of the bowl 214 to theplasma collection bag 216, and a saline line 223 connects the outletport 224 of the bowl 214 to the saline container 217. An anticoagulantline 225 connects the anti-coagulant container 210 to the inlet line218. In addition to the components mentioned above and as shown in FIG.3 , the blood processing system 100 includes a controller 226, a motor228, and a centrifuge chuck 230. The controller 226 is operably coupledto the two pumps 232 and 234, and to the motor 228, which, in turn,drives the chuck 230. The controller 226 may be operably coupled to andin communication with the user interface 190.

In operation, the disposable collection set 200 (e.g., the inletdisposable set 200A and the outlet disposable set 200B) may be loadedonto/into the blood processing system 10 prior to blood processing. Inparticular, the blood/inlet line 218 is routed through the blood/firstpump 232 and the anticoagulant line 225 from the anti-coagulantcontainer 210 is routed through the anticoagulant/second pump 234. Thecentrifugation bowl 214 may then be securely loaded into the chuck 230.Once the bowl 214 is secured in place, the technician may install theoutlet disposable set 200B. For example the technician may connect abowl connector 300 to the outlet 224 of the bowl 214, install the plasmacontainer 216 into the weight senor 195, run the saline line 223 throughvalve 135, and run the plasma/outlet line 222 through valve 130 and theline sensor 185. Once the disposable set 200 is installed and theanticoagulant and saline containers 210/217 are connected, the system100 is ready to begin blood processing.

FIG. 4 is a flowchart depicting an exemplary method of collecting plasmain accordance with various embodiments of the present invention. Priorto connecting the donor to the blood processing device 100, it isbeneficial (and perhaps necessary in some instances) to obtain/determinesome information regarding the donor, namely, the donor's weight (Step410) and hematocrit (Step 415). Not only does this information helpdetermine if the individual is a viable donor and the volumes of bloodcomponents that may be withdrawn/collected (e.g., per the FDAguidelines), the hematocrit may be used during processing to helpcollect a target volume of plasma. The technician may obtain/determinethe donor's weight by weighing the donor (e.g., on a scale). Toobtain/determine the donor's hematocrit, the technician may draw a bloodsample from the donor and test the sample of blood. Additionally oralternatively, as discussed in greater detail below, the system maydetermine the hematocrit during blood processing. For example, the bloodprocessing device 100 may include a hematocrit sensor (not shown) thatdetermines the hematocrit of the blood flowing into the blood processingdevice 100 and/or the system 100 may determine the hematocrit based on avolume of red blood cells collected within the bowl 214.

Once the lines 222/223 are in place and the technician has determinedthe donor's weight and/or hematocrit (if needed), the user/technicianmay insert the venous access device 206 into the donor's arm 208 (Step420). Next, the controller 226 activates the two pumps 232, 234 and themotor 228. Operation of the two pumps 232, 234 causes whole blood to bedrawn from the donor (step 425), anticoagulant from container 210 to beintroduced into the drawn whole blood (step 430), and the nowanticoagulated whole blood to be delivered to the inlet port 220 of thebowl 214.

It should be noted that the anticoagulant line 225 may also include abacteria filter (not shown) that prevents any bacteria in theanticoagulant source 210, the anticoagulant, or the anticoagulant line225 from entering the system 100 and/or the subject. Additionally, theanticoagulant line 225 may include an air detector 140 that detects thepresence of air within the anticoagulant. The presence of air bubbleswithin any of the system 100 lines can be problematic for the operationthe system 100 and may also be harmful to the subject if the air bubblesenter the blood stream. Therefore, the air detector may be connected toan interlock that stops the flow within the anticoagulant line 225 inthe event that an air bubble is detected (e.g., by stopping theanticoagulant pump 234), thereby preventing the air bubbles fromentering the subject.

As the anti-coagulated whole blood is withdrawn from the subject andcontained within the blood component separation device 214, the bloodcomponent separation device 214 separates the whole blood into severalblood components (Step 435). For example, the blood component separationdevice 214 may separate the whole blood into a first, second, third,and, perhaps, fourth blood component. More specifically, the bloodcomponent separation device 214 (and the centrifugal forces created byrotation of the separation device 214) can separate the whole blood intoplasma, platelets, red blood cells (“RBC”), and, perhaps, white bloodcells (“WBC”). The higher density component, i.e., RBC, is forced to theouter wall of the bowl 214 while the lower density plasma lies nearerthe core. A buffy coat is formed between the plasma and the RBC. Thebuffy coat is made up of an inner layer of platelets, a transitionallayer of platelets and WBC and an outer layer of WBC. The plasma is thecomponent closest to the outlet port and is the first fluid componentdisplaced from the bowl 214 via the outlet port 224 as additionalanticoagulated whole blood enters the bowl 214 through the inlet port220.

As shown in FIG. 3 , the system 100 may also include an optical sensor213 that may be applied to a shoulder portion of the bowl 214. Theoptical sensor monitors each layer of the blood components as theygradually and coaxially advance toward the core from the outer wall ofthe bowl 214. The optical sensor 213 may be mounted in a position (e.g.,within the well 180) at which it can detect the buffy coat and/or thered blood cells reaching a particular radius, and the steps of drawingthe whole blood from the subject/donor and introducing the whole bloodinto the bowl 12 may be altered and/or terminated in response to thedetection.

Additionally, in some embodiments, the optical sensor 213 may be used todetermine the hematocrit of the donor during processing. For example, asthe bowl 214 fills with red blood cells and the optical sensor 213detects the layer of red blood cells, the system 100 (e.g., thecontroller) can determine the volume of red blood cells within bowl 214based on the location of the red blood cell layer and the fixed/knownbowl volume. The system 100 may then calculate the donor hematocritbased on the volume of red blood cells within the bowl and the volume ofwhole blood that has been processed to that point.

Once the blood component separation device 214 has separated the bloodinto the various components, one or more of the components can beremoved from the blood component separation device 214. For instance,the plasma may be removed to a plasma container 216 (e.g., a plasmabottle) through line 222 (Step 440). As noted above, some embodiments ofthe system 100 may include a weight sensor 195 (FIG. 1 ) that measuresthe amount of plasma collected. The plasma collection process maycontinue until the a target volume of pure plasma (discussed in greaterdetail below) is collected within the plasma collection container 216.Although not shown, if the blood processing system 100 and/or thedisposable set 200 include platelet, red blood cell, and/or white bloodcell bags, each of the bags/containers may include similar weightsensors (e.g., load cells).

In some embodiments, the system 100 may also include a line sensor 185(mentioned above) that can determine the type of fluid (e.g., plasma,platelets, red blood cells etc.) exiting the blood component separationdevice 214. In particular, the line sensor 185 consists of an LED whichemits light through the blood components leaving the bowl 214 and aphoto detector which receives the light after it passes through thecomponents. The amount of light received by the photo detector iscorrelated to the density of the fluid passing through the line. Forexample, if plasma is exiting the bowl 214, the line sensor 185 will beable to detect when the plasma exiting the bowl 214 becomes cloudy withplatelets (e.g., the fluid existing the bowl 214 is changing from plasmato platelets). The system 100 may then use this information to eitherstop the removal of blood components from the bowl 214, stop drawingwhole blood from the subject, or redirect the flow by, for example,closing one valve an opening another.

It is important to note that during processing, the osmolarity of thered blood cells prevents the anticoagulant introduced into the wholeblood from entering/remaining with the red blood cells (e.g., within thebowl 214). Rather, the anticoagulant mixes with the plasma component.Therefore, the anticoagulant exits the bowl 214 with the plasma and iscollected within collection container 216 along with the plasma. Inother words, the weight of the product measured by the weight senor 195is the weight of the plasma, as well as any anticoagulant that is mixedwith the plasma—the weight provided by the weight sensor 195 is not theweight of pure plasma.

Additionally, whole blood contains a variable amount of plasma, asdetermined by the donor's hematocrit. The hematocrit for typical donorscan vary from 38% to 54%, which means that for 100 ml of whole blood,the volume of plasma can vary from 36 to 62 ml. Furthermore, the amountof anticoagulant added to the withdrawn whole blood is fixed (e.g., itdoes not depend on the hematocrit of the donor), meaning that thepercentage of anticoagulant in the collected plasma may vary from 9.7%to 12.7% for donor hematocrits between 38% to 54%, respectively.Therefore, not only does the volume measured by the weight sensor 195include the volume of anticoagulant, that volume of anticoagulant mayvary from donor to donor based on the hematocrit.

As mentioned above, some embodiments of the present invention continuethe blood processing/separation procedure until a target volume of pureplasma (e.g., plasma only—without the volume of any anticoagulant mixedwith the plasma included in the target volume) is collected within theplasma collection container 216. To that end, some embodiments of thepresent invention may calculate the volume of pure plasma within theplasma collection container 216. For example, the technician or thesystem 100 (e.g., the controller) may calculate the percentage ofanticoagulant within the collected plasma (Step 455) (e.g., the plasmacontained within the plasma collection container 216) based on theamount of anticoagulant added/metered into the whole blood and thehematocrit of the donor. The technician and/or system can calculate thepercentage of anticoagulant according to the following equation, whereAC is the amount of anticoagulant added to the system 100. As notedabove, because the osmolarity of the red blood cells prevents theanticoagulant from mixing with it, essentially all of the anticoagulantexits the bowl 214 and is collected within the plasma collectioncontainer 216 along with the plasma.

${\% AC} = \frac{1}{1 + {( {{AC} - 1} )( {1 - {Hct}_{D}} )}}$

The amount of anticoagulant that is added to the system 100 can bedetermined in a number of ways. For example, the system 100 can base theamount of anticoagulant (e.g., the value of “AC” in the above equation)on the predetermined ratio of anticoagulant per unit of anticoagulatedwhole blood. In some embodiments, the value of “AC” may be the inverseof the predetermined ratio (e.g., “AC” would be 16 if the ratio ofanticoagulant to anticoagulated whole blood was 1:16). Additionally oralternatively, the technician/system 100 can monitor the volume ofanticoagulant added to the system. In such embodiments, thetechnician/system can monitor the volume of anticoagulant added to thesystem 100 based on the number of rotations of the anticoagulant pump(e.g., each rotation of the anticoagulant pump introduces a set volumeof anticoagulant into the system 100) and/or based on the change inweight of the anticoagulant container 210 as measured by a weight sensor(discussed in greater detail below).

Once the technician/system 100 has calculated the percentage ofanticoagulant within the plasma collection container 216, thetechnician/system 100 may then use this information to calculate thevolume of pure plasma within the plasma collection container 216 (Step465). For example, the technician/system 100 may determine the volume ofanticoagulant within the container (based on the percentage ofanticoagulant within the container 216) and subtract this volume fromthe total volume of fluid within the container 216 as measured by theweight sensor 195. The system 100 may continue to monitor the volume ofpure plasma collected within the container 216 and continue processingwhole blood (e.g., continue performing Steps 425, 430, 435, 440, 455,460 and 465) until a target volume of pure plasma is collected withinthe plasma collection container 216 (Step 470) (e.g., 800 mL for anadult donor weighing more than 175 pounds or other limit prescribed bythe FDA or similar governing body).

Once the system 100 has collected the target volume of pure plasmawithin the plasma collection container 216, the system 100 can returnthe remaining components (e.g., the components remaining within the bowl214) to the subject (Step 475). For example, when all the plasma hasbeen removed and the bowl 214 is full of RBCs (and any other bloodcomponent not collected), the controller 226 stops the draw of wholeblood from the subject and reverses the direction of the blood/firstpump 232 to draw the RBCs (and other components) from the bowl 214directly back to the subject. Alternatively, if the system 100 is soequipped, the system may return the components to the subject via adedicated return line.

In addition to the non-collected blood components (e.g., the componentsremaining in the bowl 214), the system 100 may also return saline to thepatient/subject. The saline may be used as a compensation fluid to makeup for the volume of the blood component (e.g., plasma) that was removedand collected, and is not being returned to the patient. To that end,during the return step (e.g., Step 475), the saline valve 135 may beopened to allow saline from the saline container 217 to flow through thesaline line 223 and into the bowl 214 (via outlet 224), where it can bereturned to the patient/donor with or after the remaining bloodcomponents.

It should be noted that some embodiments may perform some additional andoptional steps to help determine the volume of pure plasma within theplasma collection container 216. For example, as mentioned above, someembodiments may monitor the change in weight of the anticoagulantcontainer 210 (e.g., as measured by a weight sensor/load cell on theanticoagulant container 210) (step 445). This measurement provides anindication of the volume of anticoagulant that has been added to thesystem 100, and may be used help determine the percentage ofanticoagulant within the plasma collection container 216. Additionallyor alternatively, some embodiments may similarly, monitor the change inweight and/or volume of the plasma and anticoagulant collected withinthe plasma collection container 216 (e.g., via weight sensor 195) (step450). This measurement may be used to calculate of the total volume ofpure plasma collected within the plasma collection container 216 (e.g.,to obtain the total weight from which to subtract the calculated volumeof anticoagulant).

Some embodiments may also (optionally) monitor the volume ofanticoagulant remaining in the bowl 214 (step 460) (e.g., anticoagulantthat did not mix with the plasma and/or otherwise remained in the bowl).For example, the system 100 may utilize the optical sensor on the bowl214 to determine whether any anticoagulant remains within the bowl 214.If it does, the method 400/system 100 may modify the calculation of theamount of pure plasma collected within the plasma collection container(e.g., either increase the calculated amount or decreased the calculatedamount), based on the volume of anticoagulant remaining within the bowl214.

Various embodiment of the present invention provide numerous benefitsover prior art plasma collection systems. In particular, as noted above,prior art plasmapheresis devices end plasma collection based on a totalvolume of anticoagulated plasma (e.g., pure plasma plus the addedanticoagulant). Although this is the easiest method because it requiresonly that the product collection container be weighed, the amount oftrue product—the pure plasma—is dependent on the donor's hematocrit. Inother words, prior art systems will collect more plasma from lowhematocrit donors than from high hematocrit donors because of thevariation of the percentage of anticoagulant in the product. Variousembodiments of the present invention address the issues of prior artsystems by collecting a standard volume (e.g., a target volume) of pureplasma from each donor. As noted above, embodiments of the presentinvention accomplish this by using knowledge of the donor's hematocritand the amount of anticoagulant collected within the plasma collectioncontainer 216 (e.g., by counting pump rotations and/or usingscale/weight sensors, etc.) to determine the percentage of anticoagulantin the product. Additionally, by stopping the plasma collection processbased on a volume of pure plasma collected, embodiments of the presentinvention are able to collect a greater volume of plasma as compared toprior art systems that stop based on a plasma/anticoagulant mixture.

It is also important to note that, although the various embodimentsdiscussed above are in relation to a blood processing system thatcollects plasma, the features discussed herein may be applied to anytype of blood processing system. For example, the features describedherein may be implemented on blood processing systems that collectand/or process red blood cells, platelets and/or white blood cells.

The embodiments of the invention described above are intended to bemerely exemplary; numerous variations and modifications will be apparentto those skilled in the art. All such variations and modifications areintended to be within the scope of the present invention as defined inany appended claims.

What is claimed is:
 1. A method for collecting plasma comprising: (a)determining a weight of a donor; (b) determining a hematocrit of thedonor; (c) inserting a venous-access device into the donor; (d)withdrawing whole blood from the donor through the venous-access deviceand a draw line, the draw line connected to a blood component separationdevice; (e) introducing anticoagulant into the withdrawn whole bloodthrough an anticoagulant line; (f) separating the withdrawn whole bloodinto a plasma component and at least a second blood component using theblood component separation device; (g) collecting the plasma componentfrom the blood component separation device and into a plasma collectioncontainer; (h) calculating a volume of anticoagulant in the collectedplasma component based, at least in part, upon the hematocrit of thedonor; (i) calculating a volume of pure plasma collected within theplasma collection container based, at least in part, on the calculatedvolume of anticoagulant in the collected plasma component; and (j)continuing steps (d) through (i) until a target volume of pure plasma iscollected within the plasma collection container.
 2. A method accordingto claim 1, further comprising: determining a change in volume within ananticoagulant container, the calculated volume of anticoagulant in thecollected plasma component being based, at least in part, on the changein volume within the anticoagulant container.
 3. A method according toclaim 1, further comprising: determining a volume of anticoagulantintroduced into the whole blood based on a number of rotations of ananticoagulant pump, the calculated volume of anticoagulant in thecollected plasma component being based, at least in part, on the numberof rotations of the anticoagulant pump.
 4. A method according to claim1, further comprising: determining a volume of anticoagulant within theblood component separation device, the calculated volume ofanticoagulant in the collected plasma component being based, at least inpart, on the volume of anticoagulant within the blood componentseparation device.
 5. A method according to claim 1, further comprising:monitoring a volume of plasma component collected within the plasmacollection container, the calculated volume of pure plasma collectedwithin the plasma collection container based, at least in part, on themonitored volume of collected plasma component.
 6. A method according toclaim 1, further comprising: monitoring a weight of plasma componentcollected within the plasma collection container, the calculated volumeof pure plasma collected within the plasma collection container based,at least in part, on the monitored weight of collected plasma component.7. A method according to claim 1, wherein step (b) includes monitoring avolume of red blood cells collected within the blood componentseparation device, the determined hematocrit of the donor based, atleast in part, on the monitored volume of red blood cells collectedwithin the blood component separation device and a volume of whole bloodwithdrawn from the donor.
 8. A method according to claim 1, wherein thetarget volume of pure plasma is based, at least in part, on the weightof the donor.
 9. A method according to claim 1, wherein the volume ofanticoagulant in the collected plasma component includes at least aportion of the anticoagulant introduced into the withdrawn blood and atleast a portion of a volume of anticoagulant added during a primingstep.
 10. A method according to claim 1, further comprising: returning,after collecting at least a portion of the target volume of pure plasma,the second blood component to the donor through a return line.
 11. Asystem for collecting plasma comprising: a venous-access device fordrawing whole blood from a subject and returning blood components to thesubject; a blood component separation device for separating the drawnblood into a plasma component and a second blood component, the bloodcomponent separation device having an outlet and being configured tosend the plasma component to a plasma container; a blood draw linefluidly connected to the venous-access device and configured totransport drawn whole blood to the blood component separation device,the flow through the blood draw line being controlled by a blood drawpump; an anticoagulant line connected to an anticoagulant source, theanticoagulant line configured to introduce anticoagulant into the drawnwhole blood; and a controller configured to control the operation of theblood component separation device and the blood draw pump, thecontroller configured to calculate (1) a volume of anticoagulant in thecollected plasma component based, at least in part, upon the hematocritof the subject, and (2) a volume of pure plasma collected within theplasma container based, at least in part, upon the volume ofanticoagulant in the collected plasma component, the controllerconfigured to stop the blood draw pump when a target volume of pureplasma is collected within the plasma container.
 12. A system accordingto claim 11, wherein the volume of anticoagulant in the collected plasmacomponent is based, at least in part, on a volume of anticoagulant addedto the drawn whole blood.
 13. A system according to claim 11, furthercomprising: an anticoagulant source weight sensor configured to measurethe weight of the anticoagulant source, the controller furtherconfigured to monitor a change in volume within the anticoagulant sourcebased on the measured weight of the anticoagulant source, the calculatedvolume of anticoagulant in the collected plasma component being based,at least in part, on the change in volume within the anticoagulantsource.
 14. A system according to claim 11, wherein the controller isconfigured to monitor a number of rotations of an anticoagulant pump todetermine a volume of anticoagulant introduced into the whole blood, thecalculated volume of anticoagulant in the collected plasma componentbeing based, at least in part, on the number of rotations of theanticoagulant pump.
 15. A system according to claim 11, furthercomprising: an optical sensor located on the blood component separationdevice and configured to monitor the contents of the blood componentseparation device and determine if a volume of anticoagulant remainswithin the blood component separation device, the calculated volume ofanticoagulant in the collected plasma component being based, at least inpart, on the volume of anticoagulant within the blood componentseparation device.
 16. A system according to claim 11, furthercomprising: a plasma container weight sensor configured to monitor avolume of plasma component collected within the plasma container, thecalculated volume of pure plasma collected within the plasma containerbased, at least in part, on the monitored volume of collected plasmacomponent.
 17. A system according to claim 11, further comprising: aplasma container weight sensor configured to monitor a weight of plasmacomponent collected within the plasma container, the calculated volumeof pure plasma collected within the plasma container based, at least inpart, on the monitored weight of collected plasma component.
 18. Asystem according to claim 11, further comprising: an optical sensorlocated on the blood component separation device and configured tomonitor a volume of red blood cells collected within the blood componentseparation device, the controller configured to determine the subject'shematocrit based, at least in part, upon on the monitored volume of redblood cells collected within the blood component separation device and avolume of whole blood withdrawn from the subject.
 19. A system accordingto claim 11, wherein the target volume of pure plasma is based, at leastin part, on the weight of the subject.
 20. A system according to claim11, wherein the volume of anticoagulant in the collected plasmacomponent includes at least a portion of the anticoagulant introducedinto the withdrawn blood and at least a portion of a volume ofanticoagulant added during a priming step.